Sulfonium Acid Diffusion Inhibitor for ArF Lithography
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Solution Overview
Problem
Current resist compositions for ArF lithography face challenges in achieving high resolution, low line width roughness (LWR), and critical dimension uniformity (CDU) due to acid diffusion issues, particularly in advanced microfabrication technologies like ArF immersion lithography.
Innovation Solution
A sulfonium compound with a specific structure is used as an acid diffusion inhibitor in a resist composition, combined with a polymer having acid dissociable groups and a photoacid generator, to control acid diffusion and improve lithography performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If transparent base resins are selected for high sensitivity, then transparency at 193 nm is improved, but acid diffusion increases leading to degraded pattern fidelity
Solution Approach 1:
The patent introduces a specific sulfonium compound as an intermediary substance between the transparent base resin and the photoacid generator. This compound acts as a mediator that captures diffusing acid protons through ion exchange, preventing the acid from traveling far from its generation site. The sulfonium compound has a pKa value of 6.0-10.0, making it effective at neutralizing the strong acid (pKa -1.7) generated by the PAG while maintaining compatibility with the transparent resin matrix, thus resolving the contradiction between using transparent resins and maintaining pattern fidelity.
2Length of moving object
If feature size is reduced for miniaturization, then integration density is improved, but acid diffusion becomes more detrimental to lithography performance
Solution Approach 1:
The patent applies preliminary anti-action by pre-positioning the sulfonium compound throughout the resist composition before exposure. This compound is prepared in advance with specific pKa characteristics (6.0-10.0) that enable it to immediately counteract acid diffusion as soon as the photoacid generator produces protons during exposure. By having this acid-trapping mechanism pre-established, the system prevents the harmful effects of acid diffusion before they can degrade lithography performance, allowing continued miniaturization to improved integration density.
3Manufacturing precision
If acid diffusion is suppressed to improve resolution, then pattern sharpness is improved, but mask error factor increases
Solution Approach 1:
The patent utilizes parameter changes by carefully selecting the pKa value of the sulfonium compound (6.0-10.0) to optimize the balance between acid diffusion suppression and mask error factor. This specific pKa range allows the compound to effectively capture diffusing acid protons, improving resolution and pattern sharpness. Simultaneously, the compound's molecular structure and acidity parameters are tuned to prevent excessive accumulation of trapped acid that could lead to mask error factor increases, thus resolving the contradiction through precise parameter optimization.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The sulfonium compound effectively reduces acid diffusion, resulting in improved resolution, LWR, and CDU, enhancing the overall lithography performance and pattern fidelity.
Implementation Method 1
a resist composition comprising a sulfonium compound of specific structure, a resist composition comprising the same, and a pattern forming process using the resist composition... acts as an acid diffusion inhibitor, improving resolution, LWR, and CDU by controlling acid diffusion through a mechanism involving ion exchange with photoacid generators
Data Source
AI summary
A sulfonium compound having formula (1) exerts a satisfactory acid diffusion control function wherein R1, R2 and R3 are a C1-C20 monovalent hydrocarbon group which may contain a heteroatom, p=0-5, q=0-5, and r=0-4. A resist composition comprising the sulfonium compound is processed by lithography to form a resist pattern with improved resolution, LWR, MEF and CDU.